1. Field of the Invention
The subject of the present invention is complexes containing finely-divided aluminium and zirconium in the form of a suspension, which effect particularly good perspiration reduction on human skin, and a process for their synthesis.
2. Description of the Related Art
The prior art already includes a series of patents for the synthesis of aluminium and zirconium complexes that can be used as active ingredients for antiperspirants.
In U.S. Pat. No. 2,814,584 and U.S. Pat. No. 2,814,585 (Daley), for the first time aluminium/zirconium/buffer complexes were described in which urea and glycine act as buffer components. These complexes are also known as ZAG in the case of glycine. Aluminium chlorohydrate (ACH) and ZrOCl2 solutions were taken as the starting point. In U.S. Pat. No. 2,854,382 (Grad), the possibility of using a solution of ZrO(OH)Cl as the Zr source instead of ZrOCl2 is also described. Although a broad range of Al:Zr molar ratios would have been possible, Daley only invokes a ratio of between 1.5:1 and 3.5:1. In the case of Grad, the molar ratio can lie between 0.5:1 and 3.0:1. In U.S. Pat. No. 2,906,688, Beekman et al. describe a further process for the synthesis of stable aluminium/zirconium complexes which is characterised in that it involves heating an aqueous mixture containing ZrOCl2xc3x978H2O and aluminium hydroxychloride (ACH) or aluminium trichloride/Al metal. Stable non-gelling solutions with an Al/Zr molar ratio of between 2 and 8 and a pH value of over 3 are obtained.
In their patent GB-2 144 992, Callaghan and Phipps describe the synthesis of active aluminium/zirconium complexes (ZAGs) in which they heated aqueous mixtures containing ZrO(OH)Cl, ACH and glycine with an Al/Zr/glycine ratio of 4:1:4 to 50xc2x0 C., and thus produced a ZAG complex. The composition of such a complex was given by the formula (Al2 (OH)6-y Xy)a (ZrO(OH)x Cl2-x)b neutral amino acid. The designation xe2x80x9cactivatedxe2x80x9d is supported by a newly introduced analytical method. This constitutes the usual method in polymer chemistry for determining molecular weight distribution using size-exclusion chromatography. The molecular weight distributions (polymer species distributions) thus determinable differ with the complexes according to Callaghan and Phipps from those in the aforesaid process and indicate, in the eyes of the inventors, the chemical difference of the new complexes.
A series of further patents (U.S. Pat. No. 4,775,528, U.S. Pat. No. 5,114,705, U.S. Pat. No. 5,298,640 and U.S. Pat. No. 5,486,347) were published by Callaghan et al., and include additional process parameters for the heating of the aqueous ZrO(OH)Cl, ACH and glycine mixtures, such as the separate heating of the ACH solution to shift the polymer species distribution (xe2x80x9cactivationxe2x80x9d) and to dry the reaction solutions.
The concept that the polymer species distribution could be important for effectiveness as an antiperspirant was also applied by Rosenberg et al. to the zirconium components utilised as the product in the patent AU 68983/94. The process described by him is characterised by the following steps:
Firstly, an aqueous mixture of a zirconium salt and glycine is made with a particular polymer species distribution. Next, an activated ACH solution (AACH) is made and reacted with the zirconium solution. This solution was then immediately dried by spray drying.
The table below provides an overview of the ZAG complexes that are registered for the cosmetics industry. The table was issued by the FDA in 1982 as Tentative Final Monograph for Antiperspirant Drug Products for1.
1 Translators note: This sentence, the last part of which is already in English in the German patent text, ends as reproduced here. 
It is known that the aluminium chlorohydrate complexes (ACH) have a polymer structure. These compounds are not particularly effective, i.e. they produce only a slight sweat reduction. They can, however, be altered by heat or chemical additions such that partial depolymerisation of the highly polymerised species takes place. Aluminium chlorohydrate complexes treated in this manner show enhanced effectiveness. It is possible to follow this level of depolymerisation (the xe2x80x9cactivationxe2x80x9d level) with the aid of size-exclusion chromatography (HPLC). According to known teaching, the presence of particular bands in the HPLC spectrum provides information as to whether these compounds have particularly good sweat-reducing properties. In this context, the presence of the so-called Band 3 (or Kd=0.4-0.5) has proved to be particularly important. If Band 3 is large, it was taken that these compounds were particularly effective. In the ensuing period, the ratio of Band 2 to Band 3 was also regarded as an important criterion for assessing effectiveness.
In determining the degree of activation or the sweat reduction capability of Al/Zr compounds, attempts were made to transfer experience gained and methods used in the field of AACH compounds. Al/Zr compounds also show a characteristic band distribution in an HPLC chromatogram.
Some researchers have also used Raman and IR spectroscopy to be able to give the bonding details and the effectiveness of these complexes.
Apart from these physical methods, the best means for determining the activation level and effectiveness is the in vitro methodxe2x80x94the so-called xe2x80x9chot-roomxe2x80x9d test, various versions of which are described (A. J. Parisse, in Cosmetic Science and Technology Series, vol. 8, xe2x80x9cClinical Safety and Efficacy Testing of Cosmeticsxe2x80x9d, p. 163-223). Commercially available activated Al/Zr complexes (antiperspirant powders) have better effectiveness than the Zr-free ACH types, although the sweat reduction values achievable are too low for the users"" requirements. There was therefore a need for more effective types. There was also a need for stable Al/Zr antiperspirant active agents in a fluid, though not aqueous, form.
In the processing of the known powder-type, activated Al/Zr active agents, problems arose due to the strong tendency of the finely divided powders towards relatively severe dust formation. Therefore, in the further processing of the powder into cosmetic formulations, observing the dust limit values is an important point in preventing any endangering of the health of workers engaged in it.
It has, therefore, not previously been possible to fulfil all the cosmetic industry""s requirements with the complexes available.
Surprisingly, it was discovered that particularly effective aluminium and zirconium-containing antiperspirant agents are obtained if these active ingredients comply with the following formulae and conditions:
Ala(OH)(3-b)Xb (ZrO)c(OH)(2-d)Xd (amino acid)e
where X=a halogen, especially chlorine
and a/c=2.0 to 10.0
(a+c)/(b+d)=0.9 to 2.1
e/c=0 to 2.0
such that at least 60% of the zirconium content can be directly titrated after dissolving in about 0.1 n HCl with EDTA at pH 0.8.
These antiperspirant agents comprise non-aqueous suspensions which are characterised in that the non-aqueous phase consists of a largely unpolarised organic liquid that is not miscible with water, belonging to the substance group alkanes, isoalkanes, monofunctional alcohols, polyfunctional alcohols, fatty acid esters of mono and dibasic carboxylic acids with monofunctional and polyfunctional alcohols, polyoxyethylenes, polyoxypropylenes, polyalkoxylate ethers of alcohols, cyclic silicones, open-chained silicones and combinations of these. In particular, the non-aqueous oil phase consists of silicone oil.
According to the invention, silicone oil components used are cyclic silicones, open-chained silicones or mixtures of these.
The finely divided antiperspirant suspensions according to the invention contain glycine and/or alanine as amino acids.
Analytical determination of the zirconium content in a Zr-containing water-soluble salt is described in the literature in the Fresenius Journal of Analytical Chemistry, Vol. 246, p. 391, 1969, or in US Pharmacopoeia XXIII.
According to this, the Al/Zr complex must be boiled for a long period in strong acid (for digestion). In this way, hydrolysis of the zirconium is reduced, because otherwise, too little zirconium would be found (see also the quote in the Fresenius Journal). It has been found that it is possible, in order to distinguish the active agents according to the invention from the standard complexes, to use a modified analysis process in addition, which differs from the standard procedure outlined above.
This modified procedure is characterised by the following steps:
A small quantity (1 g) of the suspension according to the invention is mixed with 50 ml distilled water in a beaker. The pH value of this mixture is then adjusted to 0.8 with several drops of a 10% salt solution and the solution stirred for 10 minutes. During this time, the Al/Zr compound passes into the aqueous phase and the oil phase separates out.
Next, the EDTA solution is added (20 ml, 0.05 N) and following heating to exactly 50xc2x0 C., the indicator is added and, before cooling to 40xc2x0 C., the excess EDTA is titrated back with, for example, an adjusted 0.05 n ZrOCl2 solution (to point of change from yellow to violet or orange to red).
The process for synthesis of finely dispersed antiperspirant suspensions is characterised in that an aluminium salt effective as an antiperspirant is mixed, possibly in the presence of the amino acid, preferably glycine, and with exclusion of moisture in a non-aqueous oil phase, and subsequently ground.
In the process according to the invention, an aluminium salt usable as an antiperspirant is a basic aluminium halide of the following composition:
Al(OH)(3-b)Xb
where X=halogen, especially chlorine
and b=0.4 to 3, preferably b=0.45 to 1.0
In the presence of an amino acid an aluminium salt effective as an antiperspirant with the following composition is utilised:
Al(OH)(3-b)Xb (amino acid)
where X=halogen, especially chlorine
and b=0.4 to 3, preferably b=0.45 to 1.0
and the molar ratio of the amino acid to aluminium is between 0 and 1.0. Particularly preferred are aluminium complexes of the aforesaid compositions, if during their synthesis an activation step has been passed through.
In the procedure according to the invention, a zirconium salt usable as an antiperspirant is a basic zirconium halide of the following composition:
ZrO(OH)(2-d)Xd
where X=halogen, especially chlorine
and d=0.5 to 2, preferably d=0.8 to 2
In the presence of the amino acid, e.g. glycine, the formula is as follows:
ZrO(OH)(2-d)Xd (glycine)
where X=halogen, especially chlorine
d=0.5to 2, preferably d=0.8to 2
and the molar ratio of amino acid to Zr is between 0 and 2.0
Grinding of the antiperspirant suspension in the process according to the invention is characterised in that this procedure is carried out at temperatures of below 60xc2x0 C., particularly below 40xc2x0 C. The antiperspirant suspensions are advantageously used in cosmetic formulations, for instance in xe2x80x9csoft-solidsxe2x80x9d or xe2x80x9croll-onxe2x80x9ds.
The following examples assist in further elucidating the invention: